Can I import .mtl file without the corresponding .obj file to a blender project (.blend file)?
The Obj file format is made of two files. The obj part contains the mesh informations. Geometry, UV mapping, normals. The mtl file contains a primitive Phong material, including existing paths to textures.
This material settings file cannot be loaded separately, it is tied to the obj file. And it does not contain textures, just paths to the textures. Embedding textures is not supported by the obj specifications.
But you can open the mtl file in any text editor. Have a look for the map kd entries. That's the paths to the textures.